1. Field of the Invention
The present invention relates to an apparatus for, and a method of, locating a tip of a tubular element, in particular a needle, within a region, in particular the epidural space and the peritoneal cavity, of a body of a subject.
2. Brief Description of Related Developments
Epidural anaesthesia is becoming increasingly popular for a wide variety of surgical, obstetric and analgesic procedures, with indications including surgical anaesthesia, analgesia during labor and prolonged post-operative pain relief. Epidural anaesthesia requires the identification of the epidural space, which currently is performed by inserting a needle, in particular a Touhy needle, into the appropriate location in the spinal column. The epidural space is located beyond the ligamentum flavum indenting the dura, and is entered after the tip of the needle passes through the ligamentum flavum. The most commonly employed technique is the “loss of resistance” technique in which a Touhy needle, which is connected to a loss or resistance (LOR) syringe, is advanced through the layers of back tissue while actuating the syringe to apply a pressure to the contained fluid, with the location of the tip of the needle in the epidural cavity being detected by the user “feeling” the resistance to actuation of the syringe. This technique, however, requires considerable experience in order to avoid advancing the needle through the epidural space and into the dura, and is made particularly difficult by the user having to concentrate separately both on actuating the syringe and inserting the needle. Puncturing of the dura has been identified inter alia as the cause of chronic back pain.
Laparascopy is also being increasingly utilized, and requires the Identification of the peritoneal cavity, which currently is performed by the introduction of a Veress needle through the abdomen and into the peritoneal cavity for insufflation to produce pneumoperitoneum. As with the identification of the epidural space, the successful identification of the peritoneal cavity requires considerable experience. Identification of the peritoneal cavity is particularly difficult as the sharpness of the Veress needle does not readily allow for differentiation between layers of high and low resistance when passing the Veress needle through the abdominal layers. It is not uncommon to require very many attempts to identify the peritoneal cavity, often more than ten attempts. Furthermore, successful insertion of the Veress needle can only be determined on insufflation of the peritoneal cavity.
Apparatuses have been devised for use in detecting the epidural space, such as disclosed in U.S. Pat. No. 5,024,662, but these apparatuses, in utilizing elastic elements to bias the plunger of a delivery syringe do not allow for reliable identification of the epidural space.